<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>重叠元素</title>
    <style>
        img{
            position: absolute;
            left: 0px;
            top:0px;
            z-index: -1;
        }
    </style>
</head>
<body>
    <h1>This is a heading</h1>
    <img src="img/dufu.png" width="100" height="140" alt="">
    <p>因为图像元素设置了 z-index 属性值为 -1, 所以它会显示在文字之后。</p>
</body>
</html>